Method of machining rare earth alloy and method of fabricating rare earth magnet using the same

Abstract

The invention provides a method of machining a rare earth alloy at high machining preciseness and high efficiency. In a step of grinding a block of a rare earth alloy with a grinding wheel having, on a peripheral portion thereof, a grinding edge including diamond abrasive particles, a coolant with surface tension of 25 mN/m through 60 mN/m is supplied to the grinding edge with the grinding wheel rotated.

What is claimed is:  
     
       1. A method of machining a rare earth alloy comprising the steps of: 
       providing a block of the rare earth alloy;  
       rotatably supporting a grinding wheel having, on a peripheral portion thereof, a grinding edge including diamond brasive particles; and  
       grinding the block of the rare earth alloy by bringing the grinding edge into contact with the block, with the grinding wheel rotated and with a coolant having surface tension of 25 mN/m through 60 mN/m supplied to the grinding edge of the grinding wheel.  
     
     
       2. The method of machining a rare earth alloy of  claim 1 , 
       wherein the coolant includes water as a main component.  
     
     
       3. The method of machining a rare earth alloy of  claim 1 , 
       wherein the coolant includes an antifoaming agent.  
     
     
       4. The method of machining a rare earth alloy of  claim 1 , 
       wherein the coolant has pH of 9 through 11.  
     
     
       5. The method of machining a rare earth alloy of  claim 1 , 
       wherein the coolant includes a rust inhibitor.  
     
     
       6. The method of machining a rare earth alloy of  claim 1 , 
       wherein the grinding edge of the grinding wheel further includes a phenol resin and includes the diamond abrasive particles in a volume ratio of 10 through 80%.  
     
     
       7. The method of machining a rare earth alloy of  claim 1 , 
       wherein the grinding wheel has a disk-shaped base plate, the grinding edge is disposed on a peripheral portion of the base plate, and the base plate is made from a sintered hard alloy.  
     
     
       8. The method of machining a rare earth alloy of  claim 1 , 
       wherein the rare earth alloy is a R—Fe—B rare earth sintered alloy.  
     
     
       9. The method of machining a rare earth alloy of  claim 1 , 
       wherein the coolant is jetted toward the grinding edge.  
     
     
       10. The method of machining a rare earth alloy of  claim 1 , further comprising the steps of: 
       collecting sludge including grinding waste of the rare earth alloy and the coolant produced in the step of grinding the block; and  
       separating the grinding waste of the rare earth alloy from the collected sludge by using a magnet.  
     
     
       11. The method of machining a rare earth alloy of  claim 1 , 
       wherein the step of grinding the block includes a step of moving the grinding wheel relatively to the block, whereby the block is cut into pieces.  
     
     
       12. The method of machining a rare earth alloy of  claim 1 , 
       wherein, in the step of grinding the block, a rotating speed of the grinding wheel, a cutting speed and a pressure for jetting the coolant are adjusted, whereby a force Fx along a tangent of the grinding wheel and a force Fz along a radial direction of the grinding wheel applied to the block respectively fall within predetermined ranges.  
     
     
       13. The method of machining a rare earth alloy of  claim 12 , further comprising the steps of: 
       monitoring the force Fx and the force Fz; and  
       determining whether or not the force Fx and the force Fz respectively are within the predetermined ranges.  
     
     
       14. A method of machining a rare earth alloy comprising the steps of: 
       providing a block of the rare earth alloy;  
       rotatably supporting a grinding wheel having, on a peripheral portion thereof, a grinding edge including diamond abrasive particles; and  
       grinding the block of the rare earth alloy by bringing the grinding edge into contact with the block, with the grinding wheel rotated and with a coolant having a coefficient of dynamic friction against the rare earth alloy of 0.1 through 0.3 supplied to the grinding edge of the grinding wheel.  
     
     
       15. The method of machining a rare earth alloy of  claim 14 , 
       wherein the coolant includes water as a main component.  
     
     
       16. The method of machining a rare earth alloy of  claim 14 , 
       wherein the coolant includes an antifoaming agent.  
     
     
       17. The method of machining a rare earth alloy of  claim 14 , 
       wherein the coolant has pH of 9 through 11.  
     
     
       18. The method of machining a rare earth alloy of  claim 14 , 
       wherein the coolant includes a rust inhibitor.  
     
     
       19. The method of machining a rare earth alloy of  claim 14 , 
       wherein the grinding edge of the grinding wheel further includes a phenol resin and includes the diamond abrasive particles in a volume ratio of 10 through 80%.  
     
     
       20. The method of machining a rare earth alloy of  claim 14 , 
       wherein the grinding wheel has a disk-shaped base plate, the grinding edge is disposed on a peripheral portion of the base plate, and the base plate is made from a sintered hard alloy.  
     
     
       21. The method of machining a rare earth alloy of  claim 14 , 
       wherein the rare earth alloy is a R—Fe—B rare earth sintered alloy.  
     
     
       22. The method of machining a rare earth alloy of  claim 4 , 
       wherein the coolant is jetted toward the grinding edge.  
     
     
       23. The method of machining a rare earth alloy of  claim 14 , further comprising the steps of: 
       collecting sludge including grinding waste of the rare earth alloy and the coolant produced in the step of grinding the block; and  
       separating the grinding waste of the rare earth alloy from the collected sludge by using a magnet.  
     
     
       24. The method of machining a rare earth alloy of  claim 14 , 
       wherein the step of grinding the block includes a step of moving the grinding wheel relatively to the block, whereby the block is cut into pieces.  
     
     
       25. The method of machining a rare earth alloy of  claim 14 , 
       wherein, in the step of grinding the block, a rotating speed of the grinding wheel, a cutting speed and a pressure for jetting the coolant are adjusted, whereby a force Fx along a tangent of the grinding wheel and a force Fz along a radial direction of the grinding wheel applied to the block respectively fall within predetermined ranges.  
     
     
       26. The method of machining a rare earth alloy of  claim 25 , further comprising the steps of: 
       monitoring the force Fx and the force Fz; and  
       determining whether or not the force Fx and the force Fz respectively are within the predetermined ranges.  
     
     
       27. A method of fabricating a rare earth magnet comprising the steps of: 
       providing a block of the rare earth alloy;  
       rotatably supporting a grinding wheel having, on a peripheral portion thereof, a grinding edge including diamond abrasive particles;  
       grinding the block of the rare earth alloy by bringing the grinding edge into contact with the block, with the grinding wheel rotated, with a coolant having surface tension of 25 mN/m through 60 mN/m supplied to the grinding edge of the grinding wheel, and with the grinding wheel moved relatively to the block, whereby the block is cut into pieces; and  
       magnetizing the rare earth alloy.  
     
     
       28. A method of machining a rare earth alloy comprising the steps of: 
       providing a block of the rare earth alloy;  
       establishing a cutting motion with a grinding part including diamond abrasive particles on its periphery facing the block,  
       cutting the block of the rare earth alloy by bringing the grinding part into contact with the block, with the grinding part being moved and with a coolant having surface tension of 25 mN/m through through 60 mN/m supplied to the grinding part.  
     
     
       29. A method of machining a rare earth alloy comprising the steps of: 
       providing a block of the rare earth alloy;  
       establishing a cutting motion with a grinding part including diamond abrasive particles on its periphery facing the block,  
       cutting the block of the rare earth alloy by bringing the grinding part into contact with the block, with the grinding part being moved and with a coolant having a coefficient of dynamic friction against the rare earth alloy of 0.1 through 0.3 supplied to the grinding part.  
     
     
       30. The method of machining a rare earth alloy of  claim 28 , wherein the coolant includes an antifoaming agent. 
     
     
       31. method of machining a rare earth alloy of  claim 28 , wherein the coolant has a pH of 9 through 11. 
     
     
       32. The method of machining a rare earth alloy of  claim 28 , wherein the coolant includes a rust inhibitor. 
     
     
       33. The method of machining a rare earth alloy of  claim 28 , wherein the grinding part further includes a phenol resin and includes the diamond abrasive particles in a volume ratio of 10 through 80%. 
     
     
       34. The method of machining a rare earth alloy of  claim 28 , wherein the rare earth alloy is a R—Fe—B rare earth sintered alloy. 
     
     
       35. A method of machining a rare earth alloy comprising the steps of: 
       providing a block of the rare earth alloy;  
       establishing a cutting motion with a grinding part including diamond abrasive particles on its periphery facing the block,  
       cutting the block of the rare earth alloy by bringing the grinding part into contact with the block, with the grinding part being moved and with a coolant having a coefficient of dynamic friction against the rare earth alloy of 0.1 through 0.3 supplied to the grinding part.  
     
     
       36. The method of machining a rare earth alloy of  claim 35 , wherein the coolant includes water as a main component. 
     
     
       37. The method of machining a rare earth alloy of  claim 35 , wherein the coolant includes an antifoaming agent. 
     
     
       38. The method of machining a rare earth alloy of  claim 35 , wherein the coolant has a pH of 9 through 11. 
     
     
       39. The method of machining a rare earth alloy of  claim 35 , wherein the coolant includes a rust inhibitor. 
     
     
       40. The method of machining a rare earth alloy of  claim 35 , wherein the grinding part further includes a phenol resin and includes the diamond abrasive particles in a volume ratio of 10 through 80%. 
     
     
       41. The method of machining a rare earth alloy of  claim 35 , wherein the rare earth alloy is a R—Fe—B rare earth sintered alloy. 
     
     
       42. A method of fabricating a rare earth magnet comprising the steps of: 
       providing a block of the rare earth alloy;  
       establishing a cutting motion with a grinding part including diamond abrasive particles on its periphery facing the block,  
       cutting the block of the rare earth alloy by bringing the grinding part into contact with the block, with the grinding part being moved, with a coolant having surface tension of 25 mN/m through 60 mN/m supplied to the grinding part, and with the grinding part moved relatively to the block, whereby the block is cut into pieces; and  
       magnetizing the rare earth alloy.